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the amplitude is proportional to the heartache

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Error Propagation, Part I

the amplitude is proportional to the heartache

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Quatre hasn't come down from Sandrock yet.

Heero wonders for a second why his brain is lingering on this fact; it's not his business whether Quatre sits in his Gundam. Maybe he's updating something; he's been running tests on Zero, trying to modify it. Maybe that's what he's working on. There's an odd feeling in his gut, though, as if he should be more concerned. Instincts; he should trust them.

So Heero waits. He goes through his shutdown sequence, and takes his time, even more than usual. He skulks around for a while. And then he hikes his foot into the stirrup and hoists himself aloft, to peer into Sandrock's cockpit.

"Hello," says Quatre. His voice is quiet. Intense. "I was hoping you'd come up."

"Hn." Heero looks. Quatre's smile is even. His breathing seems normal. So why are all of Heero's nerves suddenly tense? "You could have said something."

Quatre shrugs. "There was a high enough probability that you'd figure it out," he says, and Heero realizes, oh. He's also talking to Zero.

Zero has been different for all of them, but it's even more different with Quatre. When Heero uses Wing Zero all he has to do is trust his intuition, follow his instincts, and listen to the nudges Zero is giving him: Zero works with his training, enhances the skills and reflexes that are already part of his bones. From what he has gathered, Quatre sees none of that: Zero appears to Quatre in equations and percentages, statistical improbabilities and mathematical proofs and strings of logic symbols that create possibility trees the size of space itself.

Heero comes to it more honestly; Quatre can do more with it.

It isn't jealousy that draws him to Quatre so. Heero spent a sleepless night trying to analyze his emotions, and while he still can't categorize what he feels he is very sure it isn't jealousy. Quatre is a vital strategic addition to their team, and Quatre's use of the Zero System can only be a net positive for their mission; jealousy is the incorrect word for this.

What draws Heero in time and time again is, simply, as it turns out, watching Quatre use Zero.

It’s so very different from his own experience and Heero isn’t sure how relevant it will be to his own operation as a soldier, but he feels that gaining a better understanding of Quatre will help him follow orders. And there is something about watching Quatre’s honest, open, sunlit eyes turn sharp as knives and brilliant as the edge of a diamond that makes something in Heero’s chest catch, every single time. It's a sensation he cannot yet define, and until he knows how to categorize it, he will not rest; and he doesn't know how he can categorize it without further experience of the phenomenon.

It occurs to him that he may have one word to use to describe this feeling. It doesn't describe the whole, doesn't come close to encompassing all of this, but maybe it's a good place to start. The word is curiosity. Heero tastes it in his thoughts, and is only slightly startled when something beeps and Quatre's laser-sharp attention falls onto him again.

"There was an almost equal probability," Quatre continues, as if they had been speaking the entire time, and his eyes unfocus just a little, "that you would be Trowa."

Heero says nothing. He wonders whether the softness in Quatre's voice is relief or disappointment. Trowa's newly-regained memories are a dark sharp thing between them all; Trowa has been unbalanced by it, in a way Heero has never seen him be unbalanced before. Trowa walks most things like a tightrope, like the edge of a blade, but now he's spinning wildly underneath that sea of reserve. It has yet to affect him in battle but even Heero can see it if he looks hard enough; Trowa isn’t much like Heero, but he’s enough like Heero that they can read some of the signs in each other.

Heero belatedly puts two and two together and concludes that this must be what has kept Quatre up here in Sandrock so long: he is asking Zero about Trowa.

"I didn't think Zero dealt with emotional responses," Heero says, aloud, and Quatre’s small distracted smile tells him that his intuition was correct.

"It doesn't," Quatre says, as he scrolls down one of his screens. "Or, it didn't. That's what I'm trying to do. I thought—" His eyes go vague. "One of the weaknesses of the Zero System is its interference with the pilot's stability, and emotional upheaval is one of the symptoms," he says, as if he's reciting something. "My current theory is that linking the System more closely with a pilot's emotional state and awareness will help to avoid the instability produced by the System's probability analysis. I’m letting the probability loop and the emotional analyzer work in tandem."

Heero watches Quatre think. Sometimes Heero feels like he could lose himself watching Quatre do things. He has never met anyone like Quatre Winner; it's as if an entire database in his mind is blank, full of empty pages, and he wants to scrawl Quatre's secrets on every line so that he can file them all away, answering all of these unanswered questions. Heero is just being practical. People like Quatre are a mystery to soldiers like him.

Sandrock's screens whirl and scroll with text and numbers and one of those diagrams with the branches spirals out to Heero's left. He doesn't even bother to look; some of the text is in Arabic, and the rest is logic punctuation and decimal places, things that mean nothing to a soldier who follows his orders and his gut. He thinks that's why the Zero system appears to him as a guide, or a compass, or even just a feeling; he wonders whether Quatre's experience with business spreadsheets and risk analysis have influenced the way Zero presents itself in Sandrock.

"Oh," Quatre says, as if they're continuing a conversation Heero hasn't even started. "Yes. There's a lot of math in it."

Heero doesn't even know what to say. "You see chances," Quatre explains, as if he's being helpful, his voice tilted light and almost playful. "You see futures. Right? See, I kept asking for the numbers, so it just started giving them to me raw, because it's easier to start there."

He lifts a hand to wave in Heero's direction, although his other hand continues to type away at the keys and his eyes remain locked on the fishbone diagram unfolding before him. "It's because you trust your training, see. Your instincts are a soldier's. Mine aren't, so Zero has to show me more to convince me to follow."

"You're a soldier," Heero says, although he isn't really sure what he means by it; Quatre's a fighter, yes, and he doesn't shirk the tough decisions. Heero respects his actions in battle, even if his constant orders to surrender and requests for ceasefire aren't the way he would handle things himself. He trusts his instincts and emotions; Quatre does the same. It is simply that their emotional ranges are very different. It doesn’t mean Quatre isn’t a soldier; it makes them complimentary.

"Yes, but not like you, and the Zero System was meant for a real soldier." Quatre leans over to a lever, slides it halfway up, and the screens all suddenly tint gold; something starts to hum, a low vibration Heero picks up in his bones. "That's why I thought I would try to insert an emotional modifier." And he looks up.

When Quatre Winner meets his eyes, usually, Quatre's smiling and that smile skims through Heero, leaving warmth. But this time Quatre's gaze goes directly to the base of his skull and Heero feels like something has rung him like a bell. Quatre isn't just looking at him; he's looking inside him.

"Quatre," Heero says, as concern begins to make itself known. He takes a step forward, very cautious, and strangely aware of the hot air around them, as if Quatre's gaze is a rope pulling him in.

But then Quatre blinks, and murmurs, "Interesting," and his eyes fall to the screen beside him as he taps a few keys. Heero feels strangely bereft, with Quatre's attention pulled so many places – although with the way the screens are flashing, now mapping out probability branches on spherical coordinates, he can understand; modifying the Zero System is a complicated task, and he should leave Quatre to his experiment.

Heero turns to leave; Quatre's distracted and he feels like an intruder, and this is wrong, somehow – but he hears Quatre stand up behind him and he stops, despite himself, stops long enough for Quatre to rest a gentle hand on his shoulder and say, softly, "Wait."

There's a long shuddering breath and he continues. "Wait just a minute, please, Trowa."

Heero jerks, startled, and spins around despite himself.

"Don't be angry," Quatre whispers, and it's so intimate all of a sudden, even with his eyes diamond-bright and weirdly focused on Heero's face. "You have every right to be angry with me, but I'm not sure I can bear it if you are."

Heero chokes, blinks, swallows it, and says, again, almost angrily: "Quatre."

"No?" Quatre asks, and he isn't talking to Heero. "You're right, that isn't a very good approach at all." And suddenly Quatre's eyes flicker closed, and open again, and he says to the air, "Let me try again."

Heero frowns. He wants to shake Quatre – to remind Quatre who he's speaking to – but he doesn't want to shock the other boy into further unpredictability. This is infinitely strange and Heero wants to understand what is going on; he has no idea how to proceed. "Haven't you already… spoken with Trowa?" It comes out gruff, and to his surprise, Quatre laughs.

"Once or twice," he says, "but it wasn't enough. It wasn't right. It isn't right yet. I have to fix it," and he turns back to the control panel, murmuring something. A trail of binary flickers across the screen and branches into a true-false tree. Quatre's eyes follow it, darting around it as it he's speed-reading his answers in five dimensions.

Curiosity is a good word. Fascination a more dangerous one. Possibly attraction, although Heero isn't sure how to use that word in this context. And concern is becoming a player in this game as well.

"Hmm," Quatre sings, finally, turning back; his eyes focus on Heero again. There's a lazy smile around Quatre's mouth and Heero wonders who Quatre is seeing within Zero's projection. There is a long moment, sparkling and tense between them, and Quatre seems to be lost in thought. It looks like the real Quatre, so Heero just shifts his weight a little, and waits. He can wait infinitely if he needs to, for these answers.

But then something flickers and Quatre is suddenly in motion again.

"Hey," Quatre says, soft and gentle. The smile quirks, a little more real, and suddenly Heero's heart is thudding in his chest. He doesn't have any good words for this rush, either: warmth pooling in his body, a sudden feeling that's similar to panic, except that he doesn't panic – so what is this? Expectation? Quatre takes a step closer and he's still smiling and something in Heero's chest is squeezing, tight. His mouth is strangely dry.

Quatre's hands come up to rest on his shoulders and Heero freezes, stiff, too close to Quatre in this tiny space with his strange fascination bubbling out every pore. His own training is silent because he doesn't have any of these definitions. Heero wonders what Zero would say to him, now, which instinct it would gently push him towards following. He is not prepared for this.

"Trowa," Quatre says again, almost a question, and fingers trail up Heero's neck and then bury themselves in the hair at the base of his skull, Quatre's thumb tracing his cheek. Heero could not move even if he wanted to, and he's surprised to find out that he doesn't; his instincts have weighed in, and they are on the side of wait and see what happens; gather more information before acting. So he waits.

Quatre's eyes are tracing his face, concerned and curious and still so sharp, as if he's reading Zero's predictions in every nerve beneath Heero's skin: they flick from Heero's eyes to his mouth and then back, across his cheekbones; they watch Quatre's thumb tracing its pattern along Heero's skin. Heero feels like every breath he has ever taken is caught in his lungs and it's as if Quatre has pinpointed the exact moment Heero cannot take this any longer because he closes the gap between their mouths a fraction of a second before it happens.

He can't stop himself from kissing back any more than he could stop himself from breathing.

Quatre's lips are warm and confident against his, and inviting, and Heero finds that his hand has come up to rest low on Quatre’s back when he pulls Quatre closer; the warmth of Quatre’s body pressed against his is both pleasant and distracting. Heero isn’t used to having other bodies this close to his, and he feels off-put by it: warm and heady and almost dizzy, just from the simple press of their chests. His instincts are divided: somewhere low in his skull there’s an alarm going off, telling him to back away, regain distance – but the rest of him is perfectly content to let Quatre kiss his mouth open, let Quatre’s tongue slip against his, fast and sure.

Quatre backs away, a fraction of an inch, and Heero takes long breath, trying to reassert control – over his hands, which are pressed along Quatre’s spine; over his breathing, over his entire traitorous body. But Quatre’s eyes are so bright: bright and hard like diamonds, dangerously infinite.

Heero brings a hand up to touch his lips – they feel warm, as if they’ve taken on a heat that isn’t his own – and looks his question at Quatre.

Quatre’s lips curl up in a little smile; he looks breathless, too, and there’s color in his cheeks. But his eyes are focused and as they flick over Heero’s face, Heero is reminded suddenly, with a feeling like gravity hitting in an unexpected direction, that they’re in Sandrock’s cockpit and Quatre has Zero on the brain.

“Is that—“ Quatre’s smile slips, a little, and his voice is breathy. “Is this okay, Trowa?”

The name catches Heero off-guard like a little jolt to the chest, and he manages to croak out, “I—“

“Oh,” Quatre says, “oh.” His eyes go sharp and something just behind Heero lights up on the screen; he can see the yellow glow of Zero warming Quatre’s cheeks, sparking in Quatre’s eyes. “That’s right,” Quatre murmurs. “You don’t remember us.”

“I’m not,” Heero begins, but then Quatre’s fingers come up against his lips.

“I’ll remind you,” Quatre murmurs.

The exchange doesn’t make any sense; he isn’t Trowa, and Trowa remembers everything now, and Quatre’s fingers pull Heero forward at the hips and he forgets all of these things as Quatre’s mouth meets his again. This kiss is just as sweet, just as bright: Quatre’s mouth unwinds him, slowly, and his fingers haven’t moved from the small of Quatre’s back. “It’s okay,” Quatre says against his lips, and Heero almost swallows that lie as his tongue traces Quatre’s and something delicious and hot shivers down his spine.

The full force of Quatre's smile, Quatre's lips against his – Quatre's mouth, demanding, as if he can make everything in the world right through one determined kiss – it is almost enough for Heero to throw aside that last detached part of his brain, currently piling up facts. But the facts are there. It's almost as if the Zero System is looking backwards somehow; that thought goes crooked as Quatre does something with tongue and teeth that places Heero directly in the present, his fingers splayed on Quatre's back and his heart caught in his throat.

Fact: Quatre has been trying to modify the Zero System, to explore its possibilities and limitations. Fact: Trowa definitely has his memory back. Fact: Quatre has nothing to apologize for. Fact: Zero does not usually work like this. Fact: The emotional modifier is working too well. Fact: Quatre Winner is an unbelievable kisser. Fact: Heero Yuy has no idea what is happening. Fact: Heero Yuy is not Trowa Barton.

The facts compile and Heero breaks away. His breath is coming hard and fast, and he moves his hands to Quatre's hips, and somehow he shoves a couple extra inches between them because Quatre's heat is intoxicating and mind-numbing.

Quatre looks at him, surprised. His eyes scan Heero's face, and then flick to the display screen behind as something lights up in blue; his eyebrows draw down in confusion. Quatre slowly brings up one hand to rest on Heero's chest, and then presses it to his heart, a familiar gesture; "Trowa," he breathes, "is something wrong? Did I--?"

And Heero can't think of a single other way to do this at the moment, other than speaking whatever language Zero and Quatre are conversing in behind his back. He knows it probably qualifies as dangerous, and maybe reckless, but those categorizations have never meant much to Heero: he'll do whatever he needs to get where he needs to. How else does one break apart an emotional modifier? Heero doesn’t do emotion well; but he can do action.

He steps forward, more harshly than he means; his hands come up to grip Quatre's shoulders, and he catches the golden reflection in Quatre's eyes right before his mouth descends. He kisses as if to bruise. Heero wants no confusion in this; his mouth takes Quatre's like an attack. Quatre gasps and Heero swallows it, licking the surprise from Quatre's mouth and sucking it from his lower lip.

He needs to catch Quatre off-guard, because that's where the cracks in the Zero System will start to show: so he advances even further, pressing his advantage. Quatre makes a little sound that's mostly pleased and a little shocked, and he tilts his head; Heero adjusts his own angle and the kiss suddenly hits red-hot and electric, both of their mouths moving frantically in something that's half argument and half an explosion. Heero doubts he is breathing. He realizes he has backed Quatre up against the wall of the cockpit; they're pressed together from thigh to shoulder, and Quatre's pelvis is already moving against his, the motions short and hard and burning.

Heero tears his mouth away; Quatre – panting and obviously disappointed and barely coherent – meets Heero's eyes with his own, and Heero growls low in his throat: "Does Trowa kiss you like that?"

Quatre’s breath catches in absolute startlement and he freezes.

Heero thinks maybe he has won – but Quatre breathes in and then says, almost a whisper, “But – you –“ and Heero does not let him finish; this kiss is almost more than the first: more everything, more heat and more need and he’s even more determined to shock Quatre back into reality. He grinds his hips into Quatre’s and sucks down the moan, feeling firm hardness against his groin.

“Or like this,” he manages to ask, and he pauses to look into Quatre’s face. Think, Quatre, Heero wants to say, desperately, because he does not know what he’s doing; he tries to say it with his eyes, with his fingers in Quatre’s hair, with his breath.

Quatre's eyes flicker with something, and he exhales, one long shuddering moan that's thick with a desperate want; and then the display beside them blinks and Heero sees out of the corner of his eye, for one long second, all the screens go blank: characters and tables and plots fading to the steady pale golden glow he recognizes as his Zero System—

--but then Quatre murmurs something, a name, whose name, he doesn't know, and Quatre's kissing him again, much more urgent, as if neither of them need to breathe;

--and then he has both of Quatre's wrists in one hand, pinned above his head against the wall, as his mouth descends to Quatre's neck and his free hand dives to unfasten Quatre's pants; Quatre's hips jerk against his hand, eagerly, and Quatre lets out a little moan and tries to tug his wrists away: but he's so beautiful pinned between Heero and Sandrock, and Heero unzips his fly and palms Quatre through the fabric, and he hears that moan again, deeper and more frantic;

--they're on the floor, behind Sandrock's pilot's chair: Heero's lying on his back and Quatre is above him, grinding him down into the floor; Quatre’s lips are on his neck and their bare chests against each other are nothing but fire and sensation;

--Heero's on his knees, taking Quatre’s cock into his mouth; Quatre’s hands are buried in his hair, guiding his rhythm, slow but confident in that way Quatre has with everything, never rushing: Quatre’s up against the wall of Sandrock’s cockpit and the sight of him as Heero looks up – blond head thrown back against the sleek gundanium, flush spreading down his neck, the panting of his breath audible: Heero sucks him down hard, swirling his tongue, and listens for his name;

--Quatre has him bent over the pilot’s chair, somehow; he has two fingers inside of Heero and is holding them, waiting, as Heero tries not to plead with broken breaths; Heero grips the chair as Quatre twists his fingers, slick and full inside of him, and his hips jerk despite himself as burning-hot pleasure shoots down his spine;

--he’s sitting in the chair: Quatre’s kneeling before him and his entire cock is down Quatre’s throat for the longest second in the existence of space: everything is white and hot and exploding like stars, like bullets, like bombs; Quatre slides off of him long enough to look up and that look in his eyes pins Heero to the chair, thick with all kinds of things Heero can’t translate but desperately wants;

--Quatre’s on his lap, in the chair, slowly taking Heero in – inch by agonizing inch, too slow for words, and Heero wants to slam into him but can’t move; Quatre’s position gives him all of the control, and Heero can only wait and moan as heat and slick darkness engulfs him;

--but then they’re back against the wall, Heero pressing Quatre into it as his hand fumbles into the other boy’s pants, desperate and unsure, and Quatre’s breaths are almost a sob in his ear as his own hand fumbles through Heero’s shorts.

And then the world splinters out from him, a myriad of images appearing like paths, too many for Heero to feel each one. On one path he and Quatre fumble into each other, and form an anchored partnership; in another, he turns away from Quatre, and he sees the five Gundams in an uneasy line, no longer bound to each other. On one path, he and Quatre and Trowa are all together, Trowa caught between the two of them; in another, he and Duo (Duo?) watch as Trowa shyly grabs Quatre’s hand and pulls him from a room; in a third, he and Quatre come together in a hotel, lonely and dark. And from there the paths spiral off until Heero sees: it forms one of the probability trees and reality comes back to him like a shock, like a circuit, like self-destruct. Sandrock. Zero. Quatre;

--and Quatre glances up and says, suddenly, wonderingly: “Heero--”

That’s all it takes; Quatre’s firm hand grips him through his shorts and Heero thrusts his hips blindly as he comes: the sensation of all of these images, every one more real than the last, compiles in his head like an execution and his release is white and blinding and painfully hard. And his hand is apparently around Quatre’s cock because he feels Quatre say his name again; he feels Quatre’s entire body tense and he can’t stop moving, now; he watches, curious and fascinated and attracted and all of those words as Quatre’s sharp eyes flutter shut and his mouth opens in a silent oh and he comes all over Heero’s hand and against Heero’s body.

They remain where they are; Heero’s weight may be holding Quatre upright. It may be the other way around. He doesn’t know.

Finally Quatre’s breathing goes ragged, and Quatre sags against him; Heero slowly lowers them both to the floor so that they’re kneeling, around the mess and their clothing.

Quatre looks at him and it’s just Quatre, now, his eyes full of the universe and infinitely soft. “Heero,” he breathes, like it’s an apology.

“Are you functional?” It’s all Heero can think to say and he could kick himself for it.

Quatre laughs, one breathy bark that isn’t lighthearted or funny at all. “Yes,” he says. “Now.”

Heero knows he should be asking questions, but Quatre’s face is shuttered – and yet lax; he sags against Heero in a gesture that’s only trust, and Heero finds himself pressing his lips to the top of Quatre’s head, a motion he can’t place and can’t identify. Quatre sighs, and it’s almost Heero’s name.

Heero lets him hold on a while longer.